1. Field of the Invention
The present invention relates to a method of and an apparatus for laminating disc-shaped substrates, particularly to a method of integrally laminating two disc-shaped substrates using an adhesive sheet and an apparatus for carrying out the method, namely, an apparatus for bonding the adhesive sheet body onto two disc-shaped substrates.
2. Prior Art
Computers, especially personal computers have recently become popular, and the types of storage media for use therewith have increased. These types include magnetic discs, optical discs (e.g., CD-ROM), optical magnetic discs (e.g., MO), etc. The demand for optical discs has increases recently.
A DVD is one type of optical disc, and a disc-shaped substrate that is a single plate constituting the DVD is standardized to have a thickness of 0.6 mm, an outer diameter of 120 mm, an inner diameter of its central hole of 15 mm. Since such a thin disc-shaped substrate formed of a single plate is low in mechanical strength and is easily deformable, and in view of storage capacity, two disc-shaped substrates each having the same thickness (0.6 mm) are bonded onto each other to form an integrated substrate in a practical use thereof.
Such a high density storage disc (i.e. a DVD) is generally used as a laminated structure as set forth above, but is not used as a single plate. In such a case, it is necessary that both the upper and lower disc-shaped substrates be bonded onto each other.
A series of steps have been taken to manufacture an integrated storage disc (e.g. an optical disc) by bonding two disc-shaped substrates (see FIG. 22), as in the following.
(1) a step of placing a lower disc-shaped substrate D1 on a holding table 2A; PA1 (2) a step of coating an adhesive agent R made of UV cured resin to the lower disc-shaped substrate D1; PA1 (3) a step of placing an upper disc-shaped substrate D2 on the lower disc-shaped substrate D1 to overlay the former on the latter; PA1 (4) a step of rotating the holding table 2A to develop the adhesive agent R interposed between the disc-shaped substrates D1 and D2 on the entire surfaces thereof; and PA1 (5) a step of irradiating the developed adhesive agent made of UV cured resin with UV to cure the adhesive agent. PA1 (1) preparing an adhesive sheet body S comprising a plurality of adhesive agents S2 each covered with a release paper S3; PA1 (2) peeling off the release paper S3 from the adhesive sheet body S; PA1 (3) positioning each adhesive agent S2 of the adhesive sheet body S over a lower disc-shaped substrate D1 using a positioning member; PA1 (4) pressing the adhesive sheet body S from which the release paper S3 is peeled off against the lower disc-shaped substrate D1 to allow the adhesive agent S2 adhered to the lower surface of the adhesive sheet body S to bond onto a surface of the lower substrate D1 by moving a laminating member from one end of the lower disc-shaped substrate D1 to the other end thereof; PA1 (5) peeling off the adhesive sheet body S from the adhesive agent S2 bonded onto the lower disc-shaped substrate D1 using a peeling member; PA1 (6) placing an upper disc-shaped substrate D2 on the lower disc-shaped substrate D1; and PA1 (7) pressing the upper disc-shaped substrate D2 against the lower disc-shaped substrate D1 to integrally laminate the disc-shaped substrates D1 and D2. PA1 (1) preparing an adhesive sheet body S comprising a plurality of adhesive agents S2 each covered with a release paper S3; PA1 (2) peeling off the release paper S3 from the adhesive sheet body S; PA1 (3) positioning each adhesive agent S2 of the adhesive sheet body S over a lower disc-shaped substrate D1 by inserting the tip end of the positioning member into the hole P of the adhesive sheet body S; PA1 (4) pressing the adhesive sheet body S from which the release paper S3 is peeled off to allow the adhesive agent S2 adhered to the lower surface of the adhesive sheet body S to bond or transfer onto a surface of the lower disc-shaped substrate D1 by moving a rolling laminating roller from one end of the lower disc-shaped substrate D1 to the other end thereof; PA1 (5) peeling off the adhesive sheet body S from the adhesive agent S2 bonded onto the surface of the lower disc-shaped substrate D1 in the manner that the peeling member traverses while supporting the adhesive sheet body S in a state where the adhesive sheet body S and the lower disc-shaped substrate D1 do not contact each other to keep a slight gap therebetween. PA1 (6) placing an upper disc-shaped substrate D2 on the lower disc-shaped substrate D1; and PA1 (7) pressing the upper disc-shaped substrate D2 against the lower disc-shaped substrate D1 to bond the lower disc-shaped substrate D1 and the upper disc-shaped substrate D2. PA1 A fourteenth aspect of the invention resides in a laminating apparatus for laminating disc-shaped substrates comprising a holding table (2) to place a lower disc-shaped substrate D1 thereon, supporting members (tension rollers 5A, 5B) for extending an adhesive sheet body S therebetween at a given interval over the holding table (2), a centering shaft (3) for positioning the adhesive sheet body S, a laminating roller 1 for pressing the adhesive sheet body S against the lower disc-shaped substrate D1 to bond the adhesive sheet body S onto the lower disc-shaped substrate D1 while moving on the lower disc-shaped substrate D1 from one end thereof to the other thereof, and a peeling member 4 for peeling off the adhesive sheet body S bonded onto the lower disc-shaped substrate D1 from the lower disc-shaped substrate D1.
The storage disc is manufactured by the aforementioned steps, namely, the two disc-shaped substrates D1 and D2 are bonded onto each other to form a single integrated optical disc.
However in such a bonding method, since the adhesive agent is developed in a wider range by rotating the holding table, the adhesive agent is scattered outwardly due to centrifugal force. The periphery of the storage disc is made dirty or contaminated by the spray of the adhesive agent, or the adhesive agent is scattered and lost and hence the using efficiency of the adhesive agent is lowered.
Further, there is a problem that the thickness of the adhesive layer is not at all uniform. Still further, there is another problem that the number of manufacturing steps increases to increase the manufacturing cost because of the necessity of the step of irradiating adhesive agent with UV to cure the adhesive agent.
Accordingly, a method of bonding two disc-shaped substrates using an adhesive agent without requiring the developing step of the adhesive agent as set forth above has been studied. In the bonding method using an adhesive agent, the adhesive agent is bonded onto one of two disc-shaped substrates to be bonded, thereafter the other disc-shaped substrate is overlaid on the disc-shaped substrate onto which the adhesive agent is bonded.
An adhesive agent is generally used in a state where it is bonded onto a sheeting, i.e. an adhesive sheet body forming a base member, that is, a plurality of adhesive sheets or the adhesive agents are adhered to the adhesive sheet body. Accordingly, it is very ineffective to peel off the adhesive agent adhered to the adhesive sheet body one by one manually to bond or transfer it onto the lower disc-shaped substrate when two disc-shaped substrates are bonded onto each other. Further, fine air bubbles are liable to enter between the adhesive and the lower disc-shaped substrate when manually peeling off the adhesive agent. Still further, the bonding operation of an adhesive agent needs to be automated to incorporate the bonding operation of the adhesive agent to the disc-shaped substrates into the laminating lines of the disc-shaped substrates so as to produce a series of laminating lines which are sequentially controlled as a whole. That is, it is necessary to automatically bond the adhesive agent to the disc-shaped substrate to produce continuous laminating lines.